fix routing issue for esoteric characters in gorilla/mux (#8967)

First step is to ensure that Path component is not decoded
by gorilla/mux to avoid routing issues while handling
certain characters while uploading through PutObject()

Delay the decoding and use PathUnescape() to escape
the `object` path component.

Thanks to @buengese and @ncw for neat test cases for us
to test with.

Fixes #8950
Fixes #8647

cmd/utils.go

@@ -29,6 +29,7 @@ import (
 	"io/ioutil"
 	"net"
 	"net/http"
+	"net/url"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -506,9 +507,14 @@ func ceilFrac(numerator, denominator int64) (ceil int64) {
 func newContext(r *http.Request, w http.ResponseWriter, api string) context.Context {
 	vars := mux.Vars(r)
 	bucket := vars["bucket"]
-	object := vars["object"]
-	prefix := vars["prefix"]
-
+	object, err := url.PathUnescape(vars["object"])
+	if err != nil {
+		object = vars["object"]
+	}
+	prefix, err := url.QueryUnescape(vars["prefix"])
+	if err != nil {
+		prefix = vars["prefix"]
+	}
 	if prefix != "" {
 		object = prefix
 	}